Study On Seasonal Variation Of Some Biochemical Indices Of Blood And Correlation Betweenthem And Heat-tolerance In Holstein Cows

To provide theoretical basis for confirming heat-tolerant heredity indices of cows, to acceleratebreeding process, thirty-five Holstein cows were selected and divided into two groups according to droprate of milk yield in summer as compared with the milk yield in spring, drop rate below 10% washeat-tolerant group, above 40% was heat-stress group. Potassium content in erythrocyte, Na+,K+-ATPaseactivity in erythrocyte membrane, the activity of superoxide dismutase(SOD),glutathione peroxidase(GSH-Px), and malondialdehyde (MDA) content and T3,T4 concentration in plasma were determinedboth in spring and summer. The results showed: 1. (1)Potassium content in erythrocyte in summer washigher than that in spring(P<0.01), Na+,K+-ATPase activity in summer was lower than that in spring(P<0.05); Potassium content and Na+, K+-ATPase activity of heat stress group were higher(P<0.05)andlower(P<0.05)than those of heat tolerant one respectively during two seasons.(3)Correlation: markedlynegatively correlation (r =–0.502, P<0.01)between red cell potassium and Na+,K+-ATPase activity.Markedly positively correlation(r = 0.569, P<0.01), negatively correlation (r =–0.396, P<0.05)existedbetween erythrocyte potassium, Na+,K+-ATPase activity and drop rate of milk yield in spring respectively.Markedly positively correlation(r = 0.529, P<0.05), remarkably negatively correlation(r =–0.754,P<0.01)between them in summer. Negatively correlation(r =–0.143,P=0.596), Markedly positivelycorrelation(r = 0.575, P<0.01)between rise rate of potassium content in erythrocyte, drop rate ofNa+,K+-ATPase activity and drop rate milk yield. Positively correlation(r = 0.406, P<0.01), positivelycorrelation(r = 0.336, P<0.01), negatively correlation(r =–0.551, P<0.01)between SOD activity, GSH-Pxactivity, MDA content and drop rate of milk yield. 2.(1) antioxidant indices were greatly different duringtwo seasons, the activity of SOD and GSH-Px were lower(P<0.01)in summer than that in spring, but MDAcontent in summer were higher(P<0.01)than that in spring;(2) within the same season, the antioxidantindices were different between two groups. In spring, SOD activity of heat tolerant group washigher(P<0.01)than that of heat stress one, MDA content of heat tolerant group was lower(P<0.05) than thatof heat stress one; In summer, the SOD activity and GSH-Px activity of heat tolerant group werehigher(P<0.01)than that of heat stress one, but MDA content of heat tolerant group were lower(P<0.05)thanthat of heat stress one. (3)Correlation analysis showed markedly negative correlation(r =–0.710,P<0.01), markedly negative correlation(r = ?0.316,P<0.05)existed between SOD activity, GSH-Px activityand MDA content. Markedly negative correlation(r = -0.532, P<0.01), negative correlation(r = -0.271,P=0.155), markedly positive correlation(r =0.452, P<0.05) were present between SOD activity, GSH-Pxactivity, MDA content and drop rate of milk yield in spring respectively. Negative correlation (r =–0.277,P=0.190), negative correlation (r =–0.710, P<0.01), positive correlation (r = 0.733, P<0.01) existedbetween SOD activity, GSH-Px activity, MDA content and drop rate of milk yield respectively in summer.Feebly negatively correlation(r =–0.179,P=0.403), positive correlation(r = 0.493, P<0.05), feeblypositively correlation(r = 0.126, P=0.538)existed between drop rate of SOD activity, drop rate of GSH-Pxactivity, rise rate of MDA content respectively and drop rate of milk yield. (3) Markedly positivecorrelation(r = –0.406, P<0.01), markedly positive correlation(r = 0.336,P<0.05)markedly negativecorrelation(r = -0.551, P<0.01)were present between SOD activity, GSH-Px activity, MDA content andactivity of Na+,K+-ATPase respectively. 3. (1)T3 , T4 , T3:T4 in spring was higher(P<0.05), lower,higher(P<0.01)than those in two groups in summer.(2)T3 , T4 of heat stress group were higher(P<0.05)than heat tolerant one in summer, T3:T4 was the same as above in spring(P<0.05). (3)Correlation:negatively(r =–0.545, P<0.01), negatively(r =–0.403, P<0.05), positively correlation(r =0.445, P<0.05)exist...